Download anatomy of the ear

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Anatomy of the Ear
The temporal bone houses the structure commonly known as the ear. The
temporal bone consists of an outer bony structure that is part of the skull and part of the
skull base. It meets with several other bones that are part of the skull and the skull base.
Within the temporal bone and at its varied boundaries are noted the carotid artery which
goes up into the base of the temporal bone, courses through it and exits up at the front of
the temporal bone to proceed on to give blood to the central nervous system. The jugular
vein which takes the blood back from the brain area exits at the temporal bone lower
level and courses through and indents a portion of the temporal bone (see figure 1).
In regard to what is commonly felt to be the ear, there is an outer ear, a middle ear
and an inner ear. Taking the outer ear first, we see the pinna or the ear cosmetically
speaking, which resides on the lateral temporal bone. It leads to the external auditory
canal which is part of the outer ear structure. That canal is skin lined and ends at the
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tympanic membrane, or eardrum, the outer surface of which is skin lined. The tympanic
membrane has a middle portion, which is fibrous tissue and an inner layer which is
mucous membrane, the same sort of mucous membrane, generally speaking, as occurs in
the rest of the airway, including the sinuses and the lungs. There are obviously
differences among these but they are basically mucous- producing lining cells within the
under-surface of the drum in the middle ear. Thus, the outer ear ends at the outer surface
of the tympanic membrane. The skin lining should be intact and should stop at that level.
The middle ear consists of the inner surface of
the tympanic membrane, the surrounding mucous
membrane of the air-containing middle ear in which the
ossicles or “little bones” of hearing, the malleus, incus
and stapes reside. The stapes is the smallest and is the
one that seats itself at the junction of the middle ear with the inner ear. The middle ear is
an air containing compartment.
The inner ear consists of balance organ structures and hearing organ structures.
They are in a uni-compartment fluid system. That is to say, it is a self contained unit in
which cells change motion activity into neural activity. That occurs on both the vestibular
or balance side as well as on the cochlear or hearing side. These structures are known as
the labyrinth.
Lakeshore Ear, Nose & Throat Center, PC
(586) 779-7610
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The individual nerves of the inner ear then form into the larger nerves that go
through the internal auditory canal (see diagram) and lead directly to the brain. The vast
majority of these nerve structures carry the impulses to the brain, a few carry the
impulses from the brain out to modulate the inner ear, in particular the vestibular system
of the inner ear. There is one more important nerve in this area, which goes through the
temporal bone, that is the nerve which moves your face, the facial nerve. This nerve does
not give sensation to the face, but gives motion activity to the face. It has a tortuous
course that is almost uniformly predictable within the temporal bone. It comes from the
brain thorough the internal auditory canal, goes through the middle ear just above the
stapes, just under part of the inner ear, the labyrinthine portion called the horizontal semicircular canal and exits inferiorly out of the temporal bone to gain access to the face. An
accessory portion of the aerated middle ear is the mastoid process, which is a honeycomb
process of bone that resides basically under the pinna behind the ear canal but is pointed
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to by most people by pointing behind the ear where the bony prominence is notable. This
is variably aerated, it is an area that can become infected and inflamed just as any of these
anatomic areas can. Inflammation of this structure is called mastoiditis. There is a nerve
for taste which goes through the middle ear without a bony covering which makes it
somewhat susceptible to disease processes and to surgical manipulation. Any one of these
structures noted above will be referred to during various discussions of the disease
processes that can affect the ear. It would be a good idea to refer to this either directly or
by downloading a print out of this discussion when you are looking up particular areas of
significance in regard to your particular search and your particular disease while perusing
the remainder of our web site.